These enzymes are used for the proteolytic digestion of paraffin-embedded, formalin-fixed tissues prior to staining of certain antigens by immunohistochemical methods or prior to some in situ hybridization procedures. Proteolytic digestion of formalin-fixed tissues improves accessibility of antibodies and DNA probes to target sites within the tissue. In the case of IHC, proteolytic digestion exposes certain epitopes which have been masked during fixation. In ISH procedures, accessibility of tissue DNA sequences is enhanced allowing better probe penetration and hybridization.